Proton Shuttles in CeO2/CeO2−δ Core–Shell Structure

We report a confined proton transportation in the CeO2/CeO2−δ core–shell structure to build up proton shuttles, leading to a super proton conductivity of 0.16 S cm–1 for the electrolyte and advanced fuel cell performance, 697 mW cm–2 at 520 °C. The semiconductor nature of the CeO2 (i-type) core and the CeO2−δ (n-type) shell reveals a unique proton transport mechanism based on the charged layers formed at the interface of the CeO2−δ/CeO2 heterostructure. Two key factors of this structure confine proton transport to the particle surface. The first is the high concentration of oxygen vacancies in the surface layer, which benefits proton conduction. The second is a depletion region created by the core–shell interface that allows proton migration only on the surface layer rather than into the bulk CeO2. The constrained surface region of the CeO2−δ builds up continuous proton shuttles. This work presents a new methodology and understanding for proton transport in general oxides and a new generation proton ceramic fuel cells.